title: Correspondences of hydrostatic pressure in periodontal ligament with regions of root resorption: a clinical and a finite element study of the same human teeth.
abstract: BACKGROUND
  The main objectives of this study were to generate individual finite element models of extracted human upper first premolars, and to simulate the distribution of the hydrostatic pressure in the periodontal ligament (PDL) of these models for evaluation of the risk of root resorption.
  
  
  METHODS
  The individual extracted teeth were from a previous in vivo study that investigated root resorption after application of continuous intrusive forces. The results of experimental examination and simulations were compared on these identical tooth roots. The applied force system was 0.5N and 1.0N of intrusive force.
  
  
  RESULTS
  The simulated results during intrusion of 0.5N showed regions near the apical thirds of the roots with hydrostatic pressure over the human capillary blood pressure. These regions correlated with the electron microscopies of previous studies performed in Brazil with the identical teeth. An increased force of 1.0N resulted in increased areas and magnitudes of the hydrostatic pressure.
  
  
  CONCLUSIONS
  The key parameter indicating beginning root resorption used in this study was an increased value for hydrostatic pressure in the PDL.
authors.affiliation: Department of Orthodontics, Universitätsklinikum Ulm, ZMK 4, Albert-Einstein-Allee 11, 89081 Ulm, Germany. ansgar.hohmann@uni-ulm.de
authors.forename: Ansgar
authors.initials: A
authors.lastname: Hohmann
authors.forename: Uwe
authors.initials: U
authors.lastname: Wolfram
authors.forename: Martin
authors.initials: M
authors.lastname: Geiger
authors.forename: Andrew
authors.initials: A
authors.lastname: Boryor
authors.forename: Cornelia
authors.initials: C
authors.lastname: Kober
authors.forename: Christian
authors.initials: C
authors.lastname: Sander
authors.forename: Franz Günter
authors.initials: FG
authors.lastname: Sander
mesh_terms: D001696:Biomechanical Phenomena; D001699:Biometry; D001794:Blood Pressure; D002196:Capillaries / Q000503:physiopathology; D020342:Finite Element Analysis; D006801:Humans; D006874:Hydrostatic Pressure; D066298:In Vitro Techniques; D008855:Microscopy, Electron, Scanning; D003765:Models, Dental; D009971:Orthodontics, Corrective / Q000009:adverse effects; D010513:Periodontal Ligament / Q000098:blood supply / Q000473:pathology* / Q000503:physiopathology*; D012391:Root Resorption / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology* / Q000517:prevention & control; D013314:Stress, Mechanical; D055114:X-Ray Microtomography